Sleep Disturbance Trajectories in Osteoarthritis.

BACKGROUND/OBJECTIVE: Sleep disturbance is common among adults with osteoarthritis (OA), but little is known about patterns over time. In this cohort study, we identified restless sleep trajectories and associated factors in adults with or at high risk for knee OA. METHODS: Longitudinal (2004-2014) restless sleep (≥3 nights/week) annual reports over 8 years from 4359 Osteoarthritis Initiative participants were analyzed. Group-based trajectory modeling identified heterogeneous temporal patterns. Logistic regression identified baseline health and behavioral predictors of trajectory membership. RESULTS: Four restless sleep trajectory groups were identified: good (69.7%, persistently low restless sleep probabilities), worsening (9.1%), improving (11.7%), and poor (9.5%, persistently high). Among 2 groups initially having low restless sleep prevalence, the worsening trajectory group had an increased likelihood of baseline cardiovascular disease (odds ratio [OR], 1.53; 95% confidence interval [CI], 1.01-2.33), pulmonary disease (OR, 1.48; 95% CI, 1.07-2.05), lower physical activity (OR, 1.29; 95% CI, 1.03-1.61), knee pain (OR, 1.04; 95% CI, 1.00-1.07), depressive symptoms (OR, 1.03; 95% CI, 1.01-1.06), and a decreased likelihood of better mental health (OR, 0.97; 95% CI, 0.95-0.98) at baseline. Among 2 groups initially having high restless sleep prevalence, the poor group had an increased likelihood of baseline depressive symptoms (OR, 1.03; 95% CI, 1.00-1.05). CONCLUSIONS: Four trajectories of restless sleep over 8 years were identified using data collected from over 4000 older adults aged 45 to 79 years with or at higher risk for knee OA. The presence of depressive symptoms, less physical activity, knee pain, poor mental health, cardiovascular disease, or pulmonary disease was each associated with unfavorable trajectories.

Correlates of Physical Activity During Pregnancy: A Systematic Review with Implications for Evidence-based Practice.

BACKGROUND: Numerous attempts have been made to improve women's physical activity participation during pregnancy, but activity levels remain low. AIM: To examine systematically the associations of physical activity participation during pregnancy with non-modifiable correlates (not subject to change) and modifiable theoretical correlates of physical activity. METHODS: This systematic review followed PRISMA (preferred reporting items for systematic review and meta-analysis) guidelines. It includes cross-sectional and longitudinal studies that assessed non-modifiable correlates and modifiable theoretical correlates of physical activity. Five electronic databases were searched for studies published in the English language between 2010 and 2017. An author-developed data collection tool was used to examine selected variables; effect sizes were determined; and study bias was assessed. RESULTS: Ten studies were included in the final review. Overall, effect sizes for non-modifiable correlates of physical activity were small to moderate, except for mental health (d = 1.35) and prior physical activity (d = 0.63). By contrast, modifiable theoretical correlates of physical activity (e.g., self-efficacy [d = 0.96-1.42] & intention to be physically active [d = 1.62]) had moderate to large effects in the expected direction with physical activity during pregnancy. DISCUSSION: The findings underscore the importance of developing physical activity interventions for pregnant women that are guided by modifiable theoretical correlates, taking into consideration non-modifiable correlates of physical activity. LINKING EVIDENCE TO ACTION: Clinicians should help pregnant women to increase self-confidence in their ability to be physically active and provide anticipatory guidance to overcome barriers to physical activity.

Serum adipokine levels and associations with patient-reported fatigue in systemic lupus erythematosus.

Physical activity ameliorates fatigue in systemic lupus erythematosus (SLE) patients by an unknown mechanism. Adipokines, which are influenced by adiposity and physical activity, may be associated with patient-reported fatigue. We describe cross-sectional associations between adipokines and fatigue, physical activity, and SLE disease activity. We measured adipokines, self-reported fatigue, and objective physical activity in 129 SLE patients. Fatigue was assessed with the Fatigue Severity Scale (FSS) and Patient Reported Outcomes Measurement Information System® (PROMIS®) Fatigue score. Disease activity was measured with the Safety of Estrogens in Systemic Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI). Participants wore an accelerometer for 7 days to measure physical activity. Leptin, adiponectin, and resistin were measured in stored serum with a Luminex bead-based assay. Multivariable regression models assessed relationships between fatigue and adipokines, and Spearman correlation coefficients summarized associations between adipokines, physical activity, and SELENA-SLEDAI. Median adipokine levels were: leptin 30.5 ng/ml (Interquartile Range 14.0, 56.6), adiponectin 11.6 µg/ml (7.2, 16.8) and resistin 1.4 ng/ml (1.0, 2.2). Associations between adipokines and FSS or PROMIS fatigue were not significant. Body mass index (BMI) ≥ 30 kg/m2 was associated with FSS and PROMIS fatigue in regression analyses (p < 0.05). Weak correlations between leptin, adiponectin, leptin/adiponectin (L/A) ratio, and physical activity and between adiponectin and SELENA-SLEDAI score were not significant after adjusting for BMI. Adipokines were not associated with fatigue in SLE. Adipokines were correlated with physical activity (leptin, adiponectin, L/A ratio) and SLE disease activity (adiponectin), but most of these associations were explained by BMI.

Association Between Sedentary Time and Quality of Life From the Osteoarthritis Initiative: Who Might Benefit Most From Treatment?

OBJECTIVE: To investigate the relationship between sedentary behavior and quality-adjusted life years (QALYs) among participants in the Osteoarthritis Initiative. DESIGN: Longitudinal, observational design. SETTING: Osteoarthritis Initiative cohort. PARTICIPANTS: Individuals (N=1794) from a prospective, multicenter longitudinal cohort were classified into quantile groups based on average daily sedentary time (most sedentary, quartile 1 [Q1] ≥11.6h; 10.7h≤ Q2 <11.6h; 9.7h≤ Q3 <10.7h; least sedentary, Q4 <9.7h). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Individual QALYs were estimated over 2 years from the area under the curve of health-related utility scores derived from the Medical Outcomes Study 12-Item Short-Form Health Survey versus time. The relationship between baseline sedentary behavior and median 2-year QALYs was estimated using quantile regression adjusted for socioeconomic factors and body mass index. RESULTS: Lower QALYs over 2 years were more frequently found among the most sedentary (Q1, median 1.59), and QALYs increased as time spent in baseline sedentary behavior decreased (median QALYs for Q2, 1.64; Q3, 1.65; Q4, 1.65). The relationship of sedentary time and median QALY change was only significant for the most sedentary Q1 group, where an additional hour of sedentary behavior significantly reduced QALYs by -.072 (95% confidence interval, -.121 to -.020). CONCLUSIONS: Our findings suggest that individuals with the most extreme sedentary profiles may be vulnerable to additional losses of quality of life if they become more sedentary. Targeting these individuals to decrease sedentary behavior has the potential to be cost-effective.

Patients Less Likely to Lose Weight Following a Knee Replacement: Results From the Osteoarthritis Initiative.

BACKGROUND: Knee replacement typically results in reduced pain and improved function, but it is unclear if these improvements lead to weight loss. OBJECTIVE: The purpose of this study was to examine weight change patterns preoperatively and postoperatively among overweight/obese knee replacement patients. METHODS: The study evaluated 210 overweight/obese patients from the Osteoarthritis Initiative who underwent a knee replacement during an 8-year longitudinal study. Average annual weight changes during 1- to 2-year intervals prior to, including, and subsequent to knee replacement were categorized as loss (≥-2.5%), maintain (>-2.5% to <2.5%), and gain (≥2.5%). Weight changes across time intervals were compared using logistic regression with generalized estimating equations, adjusting for demographic, health, and knee factors. RESULTS: On average, patients lost -0.6 kg/y during the interval when the surgery was performed, but weight gain (0.9 kg/y) in the initial postoperative interval represented an overall net weight gain (0.3 kg/y) compared with presurgery. Continued weight gain (0.3 kg/y) was also seen among patients with additional follow-ups. Patients were significantly less likely to have a meaningful weight loss in the time interval immediately following the surgery compared with the interval in which the surgery took place (odds ratio, 0.37; 95% confidence interval, 0.18-0.79). CONCLUSIONS: Overweight and obese patients initially lost weight during the interval including knee replacement; however, they were less likely to lose more than 2.5% of their weight in the 1 to 2 years immediately after the surgery. Knee replacement patients may benefit from weight management interventions both preoperatively and postoperatively.

Do Inactive Older Adults Who Increase Physical Activity Experience Less Disability: Evidence From the Osteoarthritis Initiative.

BACKGROUND: Physical inactivity is a leading risk factor for developing disability. Although randomized clinical trials have demonstrated improving physical activity can reduce this risk in older adults with arthritis, these studies did not specifically evaluate inactive adults. OBJECTIVES: The aim of this study was to evaluate the relationship of changes in physical activity with disability changes among initially inactive adults with or at high risk of knee osteoarthritis from Osteoarthritis Initiative. METHODS: Inactive persons were identified at baseline based on the US Department of Health and Human Services classification (no [zero] 10-minute session of moderate-to-vigorous [MV] activity over 1 week) from objective accelerometer monitoring. Two years later, physical activity change status was classified as follows: (1) met Federal physical activity guidelines (≥150 MV minutes/week acquired in bouts ≥10 minutes), (2) insufficiently increased activity (some but <150 MV bout minutes/week), or (3) remained inactive. Disability at baseline and 2 years was assessed by Late Life Disability Instrument limitation and frequency scores. Multiple regression evaluated the relationship of physical activity change status with baseline-to-2-year changes in disability scores adjusting for socioeconomics, health factors, and baseline disability score. RESULTS: Increased physical activity showed a graded relationship with improved disability scores in Late Life Disability Instrument limitation (P < 0.001) and frequency scores (P = 0.027). While increasing MV activity to guideline levels showed the greatest reduction, even insufficiently increased physical activity was related to reduced disability. CONCLUSIONS: Findings support advice to increase MV physical activity to reduce disability among inactive adults with or at high risk of knee osteoarthritis, even when guidelines are not met.

Combined Effects of Sedentary Behavior and Moderate-to-Vigorous Physical Activity on Cardiovascular Health in Older, Community-Dwelling Latinos.

This study examined the combined effects of sedentary behavior and moderate-to-vigorous physical activity (MVPA) on cardiovascular health in older Latinos. In a cross-sectional sample of 147 older, community-dwelling Latinos, time spent in sedentary behavior and MVPA were obtained using accelerometers. Analyses examined the effects of a measure of physical activity that combined levels of sedentary behavior (± 10 daily hours) and MVPA (< 30, 30-150, or > 150 weekly minutes) on cardiovascular health outcomes (blood pressure, BMI, waist circumference, cardiorespiratory fitness). Results suggest that cardiovascular health benefits of MVPA on BMI (p = .005), waist circumference (p = .002), and cardiorespiratory fitness (p = .012) may depend on a participant's level of sedentary behavior. For all three, health benefits of 30-150 weekly minutes of MVPA were found only for those without excessive sedentary behavior (≥ 10 hr). Sedentary behavior may negatively impact cardiovascular health despite moderate participation in MVPA. Health guidelines should suggest reducing sedentary behavior while increasing MVPA.

Sedentary Behavior as a Risk Factor for Physical Frailty Independent of Moderate Activity: Results From the Osteoarthritis Initiative.

OBJECTIVES: This prospective longitudinal study investigated the association between baseline objectively measured sedentary time and 2-year onset of physical frailty. METHODS: We studied 1333 Osteoarthritis Initiative participants 55 to 83 years of age who were at risk for physical frailty, as assessed via low gait speed (< 0.6 m per second) or inability to perform a single chair stand. Baseline sedentary time was assessed through accelerometer monitoring. Hazard ratios (HRs) for physical frailty onset were estimated with discrete survival methods that controlled for moderate physical activity, sociodemographic characteristics, baseline gait and chair stand functioning, and health factors. RESULTS: The incidence of physical frailty in this high-risk group was 20.7 per 1000 person-years. Greater baseline sedentary time (adjusted HR = 1.36 per sedentary hour; 95% confidence interval [CI] = 1.02, 1.79) was significantly related to incident physical frailty after control for time spent in moderate-intensity activities and other covariates. CONCLUSIONS: Our prospective data demonstrated a strong relationship between daily sedentary time and development of physical frailty distinct from insufficient moderate activity. Interventions that promote reductions in sedentary behaviors in addition to increases in physical activity may help decrease physical frailty onset.

Accelerometer-monitored sedentary behavior and observed physical function loss.

OBJECTIVES: We examined whether objectively measured sedentary behavior is related to subsequent functional loss among community-dwelling adults with or at high risk for knee osteoarthritis. METHODS: We analyzed longitudinal data (2008-2012) from 1659 Osteoarthritis Initiative participants aged 49 to 83 years in 4 cities. Baseline sedentary time was assessed by accelerometer monitoring. Functional loss (gait speed and chair stand testing) was regressed on baseline sedentary time and covariates (baseline function; socioeconomics [age, gender, race/ethnicity, income, education], health factors [obesity, depression, comorbidities, knee symptoms, knee osteoarthritis severity, prior knee injury, other lower extremity pain, smoking], and moderate-to-vigorous activity). RESULTS: This cohort spent almost two thirds of their waking hours (average=9.8 h) in sedentary behaviors. Sedentary time was significantly positively associated with subsequent functional loss in both gait speed (-1.66 ft/min decrease per 10% increment sedentary percentage waking hours) and chair stand rate (-0.75 repetitions/min decrease), controlling for covariates. CONCLUSIONS: Being less sedentary was related to less future decline in function, independent of time spent in moderate-to-vigorous activity. Both limiting sedentary activities and promoting physical activity in adults with knee osteoarthritis may be important in maintaining function.

Determinants of Physical Activity Among Black Women During Pregnancy.

OBJECTIVE: To describe associations among background determinants of physical activity, modifiable theoretical determinants of physical activity, and measures of physical activity during the second and third trimesters of pregnancy among Black women. DESIGN: Longitudinal cohort. SETTING: Medical center obstetric clinic. PARTICIPANTS: Pregnant Black women (n = 40 in second trimester, n = 38 in third trimester) METHODS: We measured background determinants (demographic and pregnancy characteristics, discrimination, and neighborhood walkability) during the second trimester. We measured modifiable theoretical determinants (self-efficacy and social support) and physical activity using self-report and device measures during the second and third trimesters. We used paired t tests to determine differences in the modifiable theoretical determinants from the second trimester to third trimester and used Pearson correlations among background and modifiable determinants and physical activity measures during the second trimester. RESULTS: Participants' physical activity levels were low during the second and third trimesters (32% and 22% met recommendation, respectively). We found no changes in self-efficacy or social support between trimesters and found no associations between these modifiable determinants and actual physical activity. We found a positive correlation between previous pregnancies and physical activity measured by devices, r(36) = .33, p = .048. Pregnancy-specific stress, r(38) = -.40, p = .013, was negatively correlated, and age, r(38) = .38, p = .017, was positively correlated with self-reported physical activity. CONCLUSIONS: Low levels of physical activity during pregnancy coupled with the absence of an association with modifiable factors affecting pregnancy physical activity indicate a need to further examine the social, cultural, and environmental determinants of physical activity.

Incorporating Expected Outcomes Into Clinical Decision-Making for Total Knee Arthroplasty.

OBJECTIVE: Expected outcomes (e.g., expected survivorship after a cancer treatment) have improved decision-making around treatment options in many clinical fields. Our objective was to evaluate the effect of expected values of 3 widely available total knee arthroplasty (TKA) outcomes (risk of serious complications, time to revision, and improvement in pain and function at 2 years after surgery) on clinical recommendation of TKA. METHODS: The RAND/University of California Los Angeles appropriateness criteria method was used to evaluate the role of the 3 expected outcomes in clinical recommendation of TKA. The expected outcomes were added to 5 established preoperative factors from the modified Escobar appropriateness criteria. The 8 indication factors were used to develop 279 clinical scenarios, and a panel of 9 clinicians rated the appropriateness of TKA for each scenario as inappropriate, inconclusive, and appropriate. Classification tree analysis was applied to these ratings to identify the most influential of the 8 factors in discriminating TKA appropriateness classifications. RESULTS: Ratings for the 279 appropriateness scenarios deemed 34.4% of the scenarios as appropriate, 40.1% as inconclusive, and 25.5% as inappropriate. Classification tree analyses showed that expected improvement in pain and function and expected time to revision were the most influential factors that discriminated among the TKA appropriateness classification categories. CONCLUSION: Our results showed that clinicians would use expected postoperative outcome factors in determining appropriateness for TKA. These results call for further work in this area to incorporate estimates of expected pain/function and revision outcomes into clinical practice to improve decision-making for TKA.

Physical activity levels and functional performance in the osteoarthritis initiative: a graded relationship.

OBJECTIVE: Physical activity improves function in adults with arthritis, but it is unknown if there is a graded relationship between physical activity and functional benefit. This study was undertaken to examine the cross-sectional and longitudinal relationship between self-reported physical activity and observed functional performance in adults with knee osteoarthritis (OA). METHODS: The Osteoarthritis Initiative cohort included 2,589 patients with knee OA (2,301 with longitudinal followup data) who were ages 45-79 years at baseline. Prospective annual functional performance was assessed for 2 years using timed 20-meter walk tests. We used linear regression to estimate differences across physical activity quartiles in subsequent function (baseline and 1-year activity predicts 1-year and 2-year function, respectively) adjusted for demographic factors (age, sex, race/ethnicity, education level, and marital status) and health factors (OA severity, knee symptoms, knee pain, knee injury, body mass index, comorbidity, depression, smoking, alcohol use, and other joint pain). RESULTS: Increasing physical activity levels had a significant graded relationship to functional performance. Adults in physical activity quartile groups from least active to most active had an average gait speed of 4.0, 4.2, 4.3, and 4.5 feet/second, respectively, at baseline (P for trend<0.001) and 4.0, 4.2, 4.3, and 4.5 feet/second, respectively, after 1 year (P for trend<0.001); increasing trends remained significant after adjusting for covariates. Findings were similar within sex and age groups. CONCLUSION: These prospective data indicate a consistent graded relationship between physical activity level and better performance in adults with knee OA. These findings support guidelines that encourage patients with arthritis who cannot attain minimum recommended physical activity to be as active as possible.

Objective physical activity measurement in the osteoarthritis initiative: Are guidelines being met?

OBJECTIVE: Osteoarthritis (OA) clinical practice guidelines identify a substantial therapeutic role for physical activity, but objective information about the physical activity of this population is lacking. The aim of this study was to objectively measure levels of physical activity in adults with knee OA and report the prevalence of meeting public health physical activity guidelines. METHODS: Cross-sectional accelerometry data from 1,111 adults with radiographic knee OA (49-84 years old) participating in the Osteoarthritis Initiative accelerometry monitoring ancillary study were assessed for meeting the aerobic component of the 2008 Physical Activity Guidelines for Americans (≥150 minutes/week moderate-to-vigorous-intensity activity lasting ≥10 minutes). Quantile regression was used to test median sex differences in physical activity levels. RESULTS: Aerobic physical activity guidelines were met by 12.9% of men and 7.7% of women with knee OA. A substantial proportion of men and women (40.1% and 56.5%, respectively) were inactive, having done no moderate-to-vigorous activity that lasted 10 minutes or more during the 7 days. Although men engaged in significantly more moderate-to-vigorous activity (average daily minutes 20.7 versus 12.3), they also spent more time in no or very-low-intensity activity than women (average daily minutes 608.2 versus 585.8). CONCLUSION: Despite substantial health benefits from physical activity, adults with knee OA were particularly inactive based on objective accelerometry monitoring. The proportions of men and women who met public health physical activity guidelines were substantially less than those previously reported based on self-reported activity in arthritis populations. These findings support intensified public health efforts to increase physical activity levels among people with knee OA.

Association of functional status with changes in physical activity: insights from a behavioral intervention for participants with arthritis.

OBJECTIVE: To analyze change over 6 months in accelerometer-measured physical activity for participants with arthritis in a physical activity promotion trial. We tested the hypothesis that participants with the highest baseline functional capacity, regardless of their intervention status, experienced the greatest increases in physical activity levels at 6-month follow-up. DESIGN: At baseline, participants were interviewed in person, completed a 5-minute timed walk, and wore a biaxial accelerometer for 1 week, with a subsequent week of accelerometer wear at 6 months. We present data on the changes in accelerometer-measured physical activity across baseline function quartiles derived from participants' walking speed. Analyses were controlled for sociodemographic, health status, and seasonal covariates as well as exposure to the study's behavioral intervention. SETTING: A Midwest academic medical center. PARTICIPANTS: Participants (N=226) with knee osteoarthritis or rheumatoid arthritis currently enrolled in the Improving Motivation for Physical Activity in Persons With Arthritis Clinical Trial. INTERVENTION: Counseling by physical activity coaches versus control group physician advice to exercise. MAIN OUTCOME MEASURE: Change in average daily counts between baseline and 6-month follow-up. RESULTS: Contrary to our hypothesis, and after controlling for other predictors of change, the lowest quartile function participants had the largest mean absolute and relative physical improvement over baseline, regardless of intervention group status. CONCLUSIONS: Participants at a higher risk of immanent mobility loss may have been more committed to improve lifestyle physical activity, reflecting the wisdom of targeting older adults at risk of mobility loss for physical activity behavior change interventions.

Motivational interviewing intervention for increasing physical activity and improving dietary behaviors: The Lupus Intervention Fatigue Trial protocol.

The Lupus Intervention Fatigue Trial (LIFT) is a prospective, randomized controlled trial to assess the effectiveness of a six-month motivational interviewing intervention program versus an educational control to reduce fatigue in persons with systematic lupus erythematosus (SLE). Participants are randomized using a stratified, 1:1 allocation design to the LIFT intervention or control arm. We plan to enroll 236 participants to achieve the target of 200 persons with six-month follow-up for the primary endpoint. Specific aims of this study are to evaluate the impact of the LIFT intervention on 1) self-reported measures of fatigue and 2) impact on accelerometer-measured physical activity. The primary study outcome is six-month change in fatigue from baseline, assessed by the Fatigue Severity Score (FSS). Additional outcomes include objective measures of physical activity, including non-sedentary behavior and moderate-to-vigorous activity (secondary outcome), and adherence to the LIFT dietary intervention, as assessed by nutrient density (diet quality) and recommended food groups/eating patterns (exploratory outcome) in persons with SLE. Intervention effectiveness will be assessed using an intention-to-treat two-arm comparison of six-month change in FSS, with one interim monitoring analysis. A two-sample independent group t-test will compare the six-month changes in FSS between the study arms. Intervention effect durability will be assessed 12-months after baseline (6 months after completion of the intervention). Enrollment began in June 2019 and is expected to end in June 2023. This study will inform future intervention strategies that promote physical activity and improved diet quality to reduce fatigue in persons with SLE.

Relationship Between Self-Reported Restless Sleep and Objectively Measured Physical Activity in Adults With Knee Osteoarthritis.

OBJECTIVE: Despite the numerous health benefits of physical activity, inactivity is endemic among adults with knee osteoarthritis (OA). Because sleep quality may be a target in order to improve physical activity behavior, we investigated the cross-sectional relationship between restless sleep and physical activity in participants with or at risk for knee OA. METHODS: We analyzed accelerometer-measured physical activity and clinical data of participants included in the Osteoarthritis Initiative (OAI). We used multiple regression analysis to evaluate physical activity for participants, who were grouped by the reported frequency of restless sleep, and adjusted for demographic and medical confounders. RESULTS: Of the 1,892 OAI participants for whom complete data were available, 300 participants (16%) reported restless sleep ≥3 days in the past week. Participants who reported restless sleep for much of the time (3-4 days/week) and most of the time (5-7 days/week) had 11.9% and 23.7% less weekly minutes of moderately vigorous activity, respectively, compared to participants who reported rarely restless sleep (<1 day/week) (P for trend 0.021). These differences persisted after accounting for age, sex, race, body mass index, medical comorbidity, and knee OA severity and pain (P for trend 0.023). Differences related to restless sleep were largely attenuated by the presence of high depressive symptoms and low energy levels. CONCLUSION: Poor sleep quality is associated with less physical activity in persons with or at risk for knee OA. Future studies are needed to determine the mechanisms of how poor sleep and physical activity are related, how energy and depression mediate these relationships, and whether interventions that improve sleep quality might result in increased physical activity.

Moving to maintain function in knee osteoarthritis: evidence from the osteoarthritis initiative.

OBJECTIVES: To investigate the association between baseline physical activity and 1-year functional performance in adults with knee osteoarthritis (OA). DESIGN: Prospective cohort study of knee OA development and progression with 1-year follow-up. SETTING: Community. PARTICIPANTS: Osteoarthritis Initiative public data on adults with knee OA (n=2274; age, 45-79y) who participated in functional performance assessments (timed 20-m walk and chair stand test) at baseline and 1-year follow-up. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: A good 1-year performance outcome (separately defined for walk time and chair stand measures) was improvement from baseline quintile or maintenance in the best quintile. RESULTS: Almost 2 in 5 persons with radiographic knee OA improved or maintained high performance at 1 year. Physical activity measured by the Physical Activity Scale for the Elderly (PASE) was significantly associated with good walk rate and chair stand outcomes (odds ratio per 40 units PASE [95% confidence interval]=1.13 [1.13, 1.17] and 1.10 [1.05, 1.15], respectively), as were participation in sports/recreational activities (1.45 [1.23, 1.71] and 1.29 [1.09, 1.51], respectively) and lifestyle activities (1.11 [1.06, 1.16] and 1.09 [1.04, 1.14], respectively). An independent protective relationship for these physical activity measures approached significance after adjusting for sociodemographic and health factors. Older adults reported the least baseline physical activity and least frequent good 1-year outcomes. CONCLUSIONS: These findings support public health recommendations to be physically active in order to preserve function for persons with knee OA. Physical activity messages should specifically target older adults whose low activity levels may jeopardize their ability to maintain functional performance.

The Relationship between Polypharmacy and Physical Activity in Those with or at Risk of Knee Osteoarthritis.

OBJECTIVES: Physical activity is associated with improved pain, functional status, and less disability in persons with knee osteoarthritis (KOA). Because polypharmacy is related to several adverse health outcomes in older persons, we hypothesized that it might also be associated with decreased physical activity in those with KOA. This study evaluates the relationship between the number of prescription medications and weekly moderate to vigorous physical activity (MVPA). DESIGN: We used hierarchical median quantile regression analysis to examine the cross-sectional association between the number of prescription medications taken in the past 30 days and the median objectively measured MVPA minutes controlling for demographic and clinical variables. SETTING: Four Osteoarthritis Initiative (OAI) recruitment centers in Providence, Rhode Island; Columbus, Ohio; Baltimore, Maryland; and Pittsburgh, Pennsylvania. PARTICIPANTS: Accelerometer monitoring occurred in 2,127 OAI participants. Of these, 1,889 participants had 4 or more days of valid physical activity monitoring data and complete medication/covariate data. Data were collected at the 48-month OAI follow-up visit (2008-2010). MEASUREMENTS: The outcome was weekly minutes of MVPA measured with an accelerometer. Number/type of prescribed medications and covariate data (age, sex, race/ethnicity, body mass index, presence of comorbidities, pain, depressive symptoms, and radiographic KOA severity) were taken from the public OAI database. Polypharmacy was defined as taking five or more prescribed medications. RESULTS: The prevalence of polypharmacy in the study population was 28.2%. Each additional prescription medication was related to a decrease of 3.6 minutes (95% confidence interval [CI] = -4.8 to -2.1) in median weekly MVPA minutes. Participants meeting the polypharmacy criterion exhibited a decrease of 12.6 minutes (95% CI = -21.2 to -4.7) in median weekly MVPA minutes compared with those not meeting the criterion. CONCLUSION: An increased number of prescription medications and polypharmacy are associated cross-sectionally with decreased MVPA in adults with KOA. Further study is necessary to establish the causal nature of this association.

Comparison of Physical Activity Measures Derived From the Fitbit Flex and the ActiGraph GT3X+ in an Employee Population With Chronic Knee Symptoms.

OBJECTIVE: We examined the accuracy of data from an affordable personal monitor (Fitbit Flex) compared with that of data from a research-grade accelerometer worn simultaneously for 7 days; high accuracy would support substitution with this less-expensive personal activity monitor in future community-based arthritis research. METHODS: Subjects (N = 35) with chronic knee symptoms were recruited for a pilot intervention study using Fitbits to increase physical activity in employees with chronic knee symptoms at an urban corporation. Subjects simultaneously wore for 7 days a Fitbit Flex (wrist-worn) and ActiGraph GT3X+ (waist-worn). Fitbit Flex data were regularly stored on a research storage service (Fitabase) by participants. Bland-Altman plots were constructed to examine the agreement between the mean daily times spent in light activity and in bouted moderate-to-vigorous physical activity (MVPA). Comparisons were calculated by matching Fitabase data from calendar days the Fitbit was worn with data from valid monitoring days (greater than or equal to 10 hours wear time) of the ActiGraph. RESULTS: Participants at baseline were mostly female (69%) and white (57%) and had a mean age of 52 years and body mass index of 32 kg/m2 . Bland-Altman analyses indicated systematic bias overall (the Fitbit overestimated both light-intensity activity and MVPA compared with the ActiGraph). The average error varied in magnitude and direction with changing activity amounts. CONCLUSION: The Fitbit Flex does not appear to be an adequate substitute for research-grade accelerometry (which represents the gold standard for objective research monitoring of all physical activity intensity levels) in this population of persons with chronic knee symptoms.

Correlates of improvement in walking ability in older persons in the United States.

OBJECTIVES: We analyzed factors associated with improvement in walking ability among respondents to the nationally representative Health and Retirement Study. METHODS: We analyzed data from 6574 respondents aged 53 years or older who reported difficulty walking several blocks, 1 block, or across the room in 2000 or 2002. We examined associations between improvement (versus no change, deterioration, or death) and baseline health status, chronic conditions, baseline walking difficulty, demographic characteristics, socioeconomic status, and behavioral risk factors. RESULTS: Among the 25% of the study population with baseline walking limitations, 29% experienced improved walking ability, 40% experienced no change in walking ability, and 31% experienced deteriorated walking ability or died. In a multivariate analysis, we found positive associations between walking improvement and more recent onset and more severe walking difficulty, being overweight, and engaging in vigorous physical activity. A history of diabetes, having any difficulty with activities of daily living, and being a current smoker were all negatively associated with improvement in walking ability. After we controlled for baseline health, improvement in walking ability was equally likely among racial and ethnic minorities and those with lower socioeconomic status. CONCLUSIONS: Interventions to reduce smoking and to increase physical activity may help improve walking ability in older Americans.